The present invention relates to multi-wall and multi-ply bags for packaging heavyweight material of various quantities, ranging in weight from 10 pounds to 50 pounds. Such bags usually are composed of at least two plies or layers so as to provide the requisite strength and resistance to moisture, as well as to impact damage during trans-shipment from the place of packaging to the place of sale. Such bags usually are closed at their top and bottom ends by either sewing or pinch sealing, the latter using an overlap with adhesive to close the open top end of the bag. Many multi-ply or multi-wall bags of the type referred to are also gusseted along their side walls to provide for expansion of the bag during filling with the product to be packaged.
One of the problems presented to the user of such heavy-duty gusseted multi-wall or multi-ply bags is the difficulty of opening them to release the contents without completely damaging the bag and its retention capacity for the balance of the contents. It is well known in the art that with heavy-duty multi-wall gusseted bags wherein the bag closure is formed by sewing, it is possible to sew the closure with stitching which lends itself to easy opening. However, such easy-opening feature of bags closed by stitching weakens the bag top closure and gives rise to easy rupture in transit and storage. Also, there are limitations as to the places where such easy-opening stitching can be applied to the bag.
With pinch seal bags, however, where the overlapping layers of each ply are so arranged that they are individually, adhesively secured to each other and pinched by conventional bag closing mechanisms to form an adhesively secured pinch seal, it has not heretofore been possible to provide a quick-opening for such bags because of the inherent and built-in strength of such pinch seal.
It has long been recognized that a multi-ply or multi-wall heavy-duty gusseted pinch seal bag preferably should also be provided with an easy opening structure, if it does not detract from or impair the impact and product retention characteristics of the bag during trans-shipment and rough handling from place of packaging to place of delivery and ultimate place of sale. This has not been possible prior to the present invention.